CHICAGO — The wrongful death trial of the Chicago police officer who killed Quintonio LeGrier continued for a fifth day Friday.

Officer Robert Rialmo shot and killed LeGrier, 19, when the teenager approached him with a baseball bat in Dec. 2015.

One of the issues at the center of the trial is whether the 19-year-old swung his bat at Rialmo and how close he got to the officer who responded to the 911 call on the night of the shooting.

The defense called an expert witness to the stand on Friday. Emanuel Kapelsohn was hired by the city to review the case.

In his testimony, he said Officer Rialmo's use of deadly force is in line with police standards. He told jurors that in his opinion, LeGrier posed a threat because he was swinging a deadly weapon as he walked toward Rialmo.

Kapelsohn also pointed out that LeGrier's father barricaded himself in his bedroom and called police to control his son.

Kapelsohn said that officers are trained to shoot in the chest, and as many times as necessary to get rid of any threats.

On Thursday, LeGrier's father Antonio LeGrier testified. He said he never told Rialmo, "You did what you had to do," after the shooting.

Earlier in the week, Rialmo testified that the teen's father came down the stairs after the shooting and repeatedly said, "You did what you had to do."

Rialmo also testified LeGrier was coming after him with a baseball bat and said he was fearful the teen would "knock his head off," so he shot him. Lawyers for the teen's family argued that LeGrier was too far to pose a direct threat to Rialmo.

Rialmo also testified that he ordered LeGrier at least 10 times to drop a bat, but that LeGrier kept approaching while swinging. The defense claims LeGrier's twisting motion explains why he was shot in his back multiple times.

LeGrier's family sued the city after LeGrier was fatally shot five times by Rialmo about 4:30 a.m. Dec. 26, 2015. The officer was responding to a disturbance call at LeGrier's father's apartment in the 4700 block of West Erie Street.

Jones, a neighbor, was also shot and killed during the incident in what police dubbed an accident.

According to the Chicago Police Department, LeGrier was swinging an aluminum baseball bat at Rialmo. A police disciplinary body later found no evidence LeGrier did so.

An autopsy revealed LeGrier had marijuana in his system. Officials said the teen had mental health problems and had had previous run-ins with police.

Two years after Jones’ shooting, city lawyers reached a tentative $16 million financial settlement with her family.

LeGrier called 911 three times the morning he was shot. In February 2016, city officials said two 911 operators were suspended without pay for failing to send police when LeGrier was shot. It wasn’t until the third call that the city’s Office of Emergency Management and Communications sent a squad car to check on the 19-year-old.